二叉树的构建与遍历完整代码c++

完整代码如下：

#include <iostream>
#include <vector>
#include <queue>
using namespace std;

struct TreeNode {
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

// 通过先序遍历和中序遍历构建二叉树
TreeNode* buildTree(vector<int>& preorder, vector<int>& inorder) {
    if (preorder.empty() || inorder.empty()) return NULL;

    int rootVal = preorder[0];
    TreeNode* root = new TreeNode(rootVal);

    int pos = 0;
    while (inorder[pos] != rootVal) pos++;

    vector<int> leftPreorder(preorder.begin() + 1, preorder.begin() + pos + 1);
    vector<int> leftInorder(inorder.begin(), inorder.begin() + pos);
    root->left = buildTree(leftPreorder, leftInorder);

    vector<int> rightPreorder(preorder.begin() + pos + 1, preorder.end());
    vector<int> rightInorder(inorder.begin() + pos + 1, inorder.end());
    root->right = buildTree(rightPreorder, rightInorder);

    return root;
}

// 先序遍历
void preorderTraversal(TreeNode* root) {
    if (!root) return;

    cout << root->val << " ";
    preorderTraversal(root->left);
    preorderTraversal(root->right);
}

// 中序遍历
void inorderTraversal(TreeNode* root) {
    if (!root) return;

    inorderTraversal(root->left);
    cout << root->val << " ";
    inorderTraversal(root->right);
}

// 后序遍历
void postorderTraversal(TreeNode* root) {
    if (!root) return;

    postorderTraversal(root->left);
    postorderTraversal(root->right);
    cout << root->val << " ";
}

// 层序遍历
void levelOrderTraversal(TreeNode* root) {
    if (!root) return;

    queue<TreeNode*> q;
    q.push(root);

    while (!q.empty()) {
        int size = q.size();
        for (int i = 0; i < size; i++) {
            TreeNode* cur = q.front();
            q.pop();
            cout << cur->val << " ";
            if (cur->left) q.push(cur->left);
            if (cur->right) q.push(cur->right);
        }
        cout << endl;
    }
}

int main() {
    vector<int> preorder = {1, 2, 4, 5, 3, 6, 7};
    vector<int> inorder = {4, 2, 5, 1, 6, 3, 7};

    TreeNode* root = buildTree(preorder, inorder);

    cout << "先序遍历结果：";
    preorderTraversal(root);
    cout << endl;

    cout << "中序遍历结果：";
    inorderTraversal(root);
    cout << endl;

    cout << "后序遍历结果：";
    postorderTraversal(root);
    cout << endl;

    cout << "层序遍历结果：" << endl;
    levelOrderTraversal(root);

    return 0;
}

其中，我们以先序遍历和中序遍历构建二叉树，然后分别实现了先序遍历、中序遍历、后序遍历和层序遍历的方法。在main函数中，我们构建了一个二叉树，并分别调用了这四种遍历方法，输出了遍历的结果。